Abstract: A network design method proceeds by generating cycles, evaluating the economics of building rings on those cycle, and building any economic rings. Generating a cycle involves picking two endpoints between which two disjoint link and node paths are desired—the two nodes selected are thus nodes on the candidate rings. Once a cycle is generated, various combinations of OADM/ADM nodes on the cycle are tried, from rings using three nodes to rings using all of the nodes on the cycle. The network design method considers a sequence of SONET/SDH and DWDM rings on each cycle generated, and compares the cost of carrying demand by SONET/SDH rings, DWDM rings, and an alternative dual-hub benchmark architecture. The ring constraints such as maximum circumference are applied before ring costs are calculated, and rings violating those constraints are eliminated from consideration.

Abstract: In a network for routing traffic from an originating node to a terminating node, it is common to provide alternate routes in order to increase the number of route choices between the originating and terminating nodes. The Bell System toll network employs a hierarchical alternate routing arrangement wherein various nodes, or control switching points (CSPs), are rank ordered for defining a process of routing calls through the network, whereby some CSPs are prohibited from routing traffic through other CSPs. Hence, known hierarchical alternate routing arrangements tend to inhibit route choices, which tends toward longer, and hence more costly, routes. Such problems tend to arise from the limited capability of electromechanical switching equipment. But with the increasing use of electronic stored program controlled CSPs, they can be solved with our alternate routing method which allows route choices without regard to network hierarchy.